Gömböc
A Gömböc is a convex, homogeneous, three-dimensional body that, when placed on a flat surface, always settles into a single stable and a single unstable equilibrium point. This means that if you place it in any random orientation, it will roll until it reaches its stable resting position, and then remain there. If nudged slightly, it will return to this position. The only other position it can rest in is an unstable equilibrium, where any tiny disturbance will cause it to roll away to the stable position.
The existence of such a shape was conjectured in the 1990s by Russian mathematicians Vladimir Arnold. It
The first physical Gömböc was constructed by hand, and later, the process was mechanized. Gömböc is a